This invention relates the technical field of an electric miter saw.
Because of the development in the construction material industry, an electric saw in the electric tools is widely used to cut metal tubes, angle irons, channel steels, various kinds of timber and stones. Hence, an electric saw has a large market, and science and technology staffs are developing various types of electric saws. A cutting width limit exists in the traditional and common electric saws.
If a workpiece is too wide, it cannot be cut by some saws. So, an electric saw with an adjustable cutting width has been developed, such as U.S. Pat. No. 5,054,352, in which a retractable slide rod mechanism is adopted. One end of the slide rod is housed under a cutting table and the other end can be rotatably connected to the lower end of a link arm by a supporting member. The upper portion of the link arm is connected to a fixed cutting member. With the extending and withdrawing movement of the slide rod under the cutting table, a cutting width can be adjusted. Of course, there are advantages of a compact configuration, a small dimension and convenience for use in that saw. There are disadvantages as well, for example, because the localization aperture beneath the cutting table is supported by a slidable extension, it is easy to shake, which can cause the inaccuracy in localization and decrease of cutting precision and needs to be improved.
A slide rod mechanism is also adopted in U.S. Pat. No. 5,862,732. One end of the slide bar is secured on the rear surface of the cutting table and on the other end is a housed a position limit member. The upper portion of the link arm is connected to a fixed cutting member while the lower portion can be rotatably connected to the supporting member. In the inner aperture of the supporting member are mounted linear ball bearings, by which the supporting member and slide rod can be rotatably connected. Therefore, the disadvantages in the last U.S. patent can be avoided, such as an easy shake, an inaccurate localization and decrease of precision. However, the slide rod secured under the cutting table gives the saw a non-beautiful and a slightly large appearance. Therefore, most of space under the cutting table cannot be utilized fully and the proportion of the machine is affected. And it can cause the reduction of the area of the cutting table that can be utilized efficiently and therefore affects the width of its cutting stroke, which are all needed to be improved.
On the other hand, there is no flexible blade guard on traditional electric saws and there exists some hidden troubles of safety. For that reason, an electric saw with a flexible blade guard is developed, for example, the flexible blade guard assembly for an electric saw with China's Patent No. 02266104.2. It includes a fixed guard with one end flexibly hinging to the link arm and a flexible one that is secured and co-axially move about the co-axes in the lower portion of the fixed guard. A link rod mechanism is connected to the flexible blade guard and the end of the link arm. The character of the link rod mechanism is that the short rod flexibly hinges to the end of the link arm and the other end on the link bar. The other end of the link arm flexibly hinges to the flexible blade guard. In the middle portion of the link rod is formed a track slot, which moves together with the localization pin in the inner side of the fixed blade guard. That represents a concept of design in which is adopted the control of opening and closing of the flexible blade guard by a link rod mechanism.
Though it is simple in configuration, low in manufacturing cost and easily implemented, some advantages have exposed in the practical application and they cannot be overcome, for example, the requirements of the process and installation of the link bar and slot are very high. If some errors appear during the process or installation, a dead center will be caused and the link rod mechanism will not be controlled flexibly or even be blocked dead, which will easily cause safety accidents during operation. In case those disadvantages are formed, it is very difficult to correct itself by means of adjustment of the installation position. So, a new flexible blade guard needs to be developed for the saw so that those disadvantages can be overcome.